1. Field of the Invention
This invention relates generally to a multifunction millimeter-wave system and, more particularly, to a multifunction millimeter-wave system that provides simultaneous and prioritized high data rate digital communications, active protection including radar tracking and surveillance, interceptor missile guidance, passive surveillance and identification friend-or-foe (IFF) interrogation for a military vehicle.
2. Discussion of the Related Art
Communications, detection, radar and imaging systems that operate using millimeter-wave radiation (30-300 GHz) provide significant advantages over other types of related systems that operate using visible light, infrared radiation and other electro-optical radiation. These advantages generally include the fact that millimeter-wave radiation can penetrate low visibility and obscured atmospheric conditions caused by many factors, such as clouds, fog, haze, rain, dust, smoke, sandstorms, etc., without severe attenuation, as would occur with other types of radiation. Particularly, millimeter-wave radiation around 35 GHz is minimally attenuated by oxygen and water vapor in the air.
Millimeter-wave radiation is also effective in passing through certain hard substances, such as wood. Also, because millimeter-wave systems operate at high frequency, the antenna apertures and other system hardware can be made very small. Thus, millimeter-wave systems are desirable for many applications, such as aircraft landing systems, collision avoidance systems, detection and tracking systems, surveillance systems, etc.
Because of the advantages discussed above, millimeter-wave systems are desirable for many military applications. The advantages of millimeter-wave systems for military applications can be summarized as providing small high gain antennas, good weather penetration, anti-jam capabilities, low probability of interception, low probability of detection, and wide-band operations.
Modern battlefield vehicles, such as armored vehicles, tanks and Humvees, employ highly sophisticated millimeter-wave systems for both offensive and defensive applications. For example, it is known to employ millimeter-wave radar detection systems providing 360xc2x0 radar beams for surveillance purposes to detect airborne threats, and radar beams to track direct fire threats based on optical sensor detections of gun flashes and plumes. Millimeter-wave guidance systems are known to direct or guide an interceptor missile to xe2x80x9ctake outxe2x80x9d a direct fire or airborne threat. It is also known to employ millimeter-wave identification friend-or-foe (IFF) interrogation systems to interrogate a battlefield party to determine whether he is friendly. In such systems, a coded millimeter-wave signal is transmitted to a party in the battlefield. If the appropriate signal is returned, then the transmitting party knows the interrogated party is friendly. Millimeter-wave communications systems are also used to transmit high rate digital data, such as video and multiple voice channels between parties. These communication systems enable mobile ad hoc networking.
The above described millimeter-wave systems have been employed on military vehicles, where each system addresses only a single function. Thus, the available real estate on the vehicle is quickly used up and the cost of all of the systems combined is great.
In accordance with the teachings of the present invention, a multifunction millimeter-wave system is disclosed. The multifunction system provides simultaneously two or more of the following functions: (1) high data rate communications including ad hoc networking; (2) active protection radar/guidance for point defense against direct fire and overhead threats; (3) active radar surveillance not related to point defense; (4) interceptor missile guidance not related to point defense; (5) IFF interrogation for a military vehicle; and (6) passive surveillance to sense millimeter-wave radiation.
The system includes a GPS receiver for identifying the position of the vehicle and a multifunction control computer that provides high level control functions for the system. The system also includes a plurality of sector sub-systems, such as three sector sub-systems each covering 120xc2x0. Each sub-system includes a steerable antenna that directs a millimeter-wave beam to a particular location within the area covered by the sector sub-system. Each sector sub-system also includes an FPGA-based modem that performs digital signal processing for the various system operations, such as signal modulation and demodulation. Each sector sub-system also includes an IF/RF transceiver, including a direct digital synthesizer, for providing signal tuning and frequency up-conversion and down-conversion. An alternate, lower cost, lower capability system can use a single FPGA-based modem and multiple steerable antennas. The modem switches to one array antenna at a time, while the other array antennas are inactive.
Each sector sub-system provides the various beams for each of radar surveillance, high data rate communications, active radar protection and surveillance, interceptor missile guidance, passive surveillance and IFF interrogation. The various functions are prioritized by the control computer, and can all be performed simultaneously based on the prioritization and time sharing.